put Generated annotation on generated code!

pom.xml

<plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-antrun-plugin</artifactId>
        <executions>
          <execution>
            <id>anonotate-proto</id>
            <phase>generate-sources</phase>
            <configuration>
              <target>
                <replaceregexp match="public(.*) class" flags="g" replace="@javax.annotation.Generated(&quot;protoc&quot;) \0">
                  <fileset dir="${project.basedir}/src/main/generated" includes="**/*.java" />
                </replaceregexp>
              </target>
            </configuration>
            <goals>
              <goal>run</goal>
            </goals>
          </execution>
        </executions>
      </plugin>